WASHINGTON — A powerful government workers’ union will end its support for the United Negro College Fund after the group accepted $25 million from the conservative powerhouse Koch brothers and the college fund’s president appeared at a Koch event.

In a letter made public Thursday, the American Federation of State, County and Municipal Employees said it will no longer partner with or raise funds for the fund, known for its iconic motto, “A mind is a terrible thing to waste.”

AFSCME President Lee Saunders said the actions of the college fund’s president “are not only deeply hostile to the rights and dignity of public employees, but also a profound betrayal of the ideals of the civil rights movement.”

The fund supports historically black colleges and universities and provides scholarships. It accepted a $25 million grant last month from Koch Industries Inc. and the Charles Koch Foundation.

The Koch brothers are major contributors to conservative causes and are often vilified by Democrats and liberals. After accepting the grant, Saunders says, UNCF President Michael Lomax spoke at a Koch brothers summit in California.

Saunders called the Koches “the single most prominent funders of efforts to prevent African-Americans from voting” and said Lomax’s appearance at their function was “a betrayal of everything the UNCF stands for.”

Lomax said the fund never had a litmus test for donors.

“While I am saddened by AFSCME’s decision, it will not distract us from our mission of helping thousands of African-American students achieve their dream of a college degree and the economic benefits that come with it,” Lomax said.

AFSCME is the nation’s largest public services employees union and has more than 1.6 million working and retired members. The union will sever its relationship with the UNCF on Sept. 1.

AFSCME gave between $50,000 and $60,000 annually to the UNCF for its AFSCME/UNCF Union Scholar Program, which has served 94 students since 2003. The program will continue, the union said, just no longer in partnership with the UNCF.